1. Field of the Invention
The present invention relates to a liquid crystal display used as a display unit of an electronic apparatus and a method of manufacturing the same.
2. Description of the Related Art
Recently, liquid crystal displays are used as monitors of television receivers and personal computers. In such applications, a display is required to have a wide viewing angle so that the display screen can be viewed in all directions. MVA (Multi-domain Vertical Alignment) liquid crystal displays are known as liquid crystal displays which can provide a wide viewing angle. An MVA liquid crystal display includes a liquid crystal having negative dielectric constant anisotropy sealed between a pair of substrates, vertical alignment films for aligning liquid crystal molecules substantially perpendicularly to surfaces of the substrates, and alignment regulating structures for regulating the direction of alignment of the liquid crystal molecules. Linear protrusions and blanks (main slits) in electrodes are used as the alignment regulating structures. When a voltage is applied, liquid crystal molecules are tilted in directions perpendicular to directions in which the alignment regulating structures extend. The alignment regulating structures are used to provide a plurality of regions which are different from each other in the aligning direction of liquid crystal molecules in each pixel, whereby a wide viewing angle is achieved.
In the case of an MVA liquid crystal display, however, since linear protrusions or main slits having a relatively great width are provided in pixel regions, the aperture ratio of the pixels becomes smaller than that in a TN mode liquid crystal display having no alignment regulating structure, which results in a problem in that high light transmittance cannot be achieved.
In order to solve the above-described problem, some MVA liquid crystal displays are provided with pixel electrodes having a cross-shaped electrode extending in parallel with or perpendicularly to bus lines, a plurality of stripe-shaped electrodes obliquely branching from the cross-shaped electrodes and extending in four orthogonal directions, and fine slits formed between stripe-shaped electrodes adjacent to each other. When a voltage is applied, liquid crystal molecules are tilted by oblique electric fields generated at edges of the pixel electrodes in directions in parallel with directions in which the fine slits extend. In the case of such an MVA liquid crystal display, any reduction in the aperture ratio can be suppressed because there is no linear protrusion or main slit having a great width in pixel regions. However, since an alignment regulating force provided by stripe-shaped electrodes and fine slits is weaker than an alignment regulating force provided by linear protrusions or main slits, a problem arises in that the liquid crystal will have a long response time and in that alignment is liable to disturbance attributable to a press with a finger.
Under the circumstance, liquid crystal displays having the above-described pixel configuration employ a polymer sustained alignment (PSA) technique for memorizing tilting directions of liquid crystal molecules by mixing a polymeric component that can be optically or thermally polymerized (a monomer or oligomer) in the liquid crystal in advance and polymerizing the polymeric component while the liquid crystal molecules are tilted by a voltage applied thereto (see Patent Document 1 for example). In a liquid crystal display employing the PSA technique, since polymer layers which memorize tilting directions of liquid crystal molecules are formed at interfaces between the liquid crystal and alignment films, a high alignment regulating force can be obtained. Thus, the liquid crystal has a short response time, and liquid crystal molecules can be reliably tilted in directions in parallel with directions in which fine slits extend. It is therefore possible to provide an MVA liquid crystal display which is less liable to disturbance of liquid crystal alignment even when pressed by a finger.
The one drop filling (ODF) method is known as a method of filling a gap between substrate with a liquid crystal. According to the ODF method, a seal material is continuously applied in the form of a frame along the periphery of one substrate; a prescribed amount of liquid crystal is dispensed inside the frame on the substrate; the substrate is combined with another substrate in vacuum; and the atmospheric pressure is restored to fill a gap between the substrates with the liquid crystal. The use of the ODF method makes it possible to complete substrate combining and liquid crystal filling substantially at the same time, which significantly simplifies steps for manufacturing a liquid crystal display.
Patent Document 1: JP-A-2003-149647
Patent Document 2: JP-A-5-281530
Patent Document 3: JP-A-9-80396
FIG. 9 is an enlarged view of the neighborhood of a part of a display screen of a liquid crystal display fabricated using the ODF method where a liquid crystal has been dispensed. As shown in FIG. 9, in the liquid crystal display fabricated using the ODF method, a display irregularity or so-called dispensing mark may be visually perceived in the part where the liquid crystal has been dispensed enclosed by a broken line. For this reason, a liquid crystal display fabricated using the ODF method has a problem in that it is difficult to achieve high display quality. In particular, the problem is significant in a liquid crystal display employing the PSA technique because a dispensing mark is more visually perceivable on the same.